Trolley drive for over and under conveyor

ABSTRACT

The main propelling member is mounted on an overhead power track for selected driving engagement with carriers suspended by trolleys on the free track. The propelling member has a depending puller arm with a socket forming integral puller and holdback dogs engageable with a drive post on the carrier. The upper surface of the socket is irregular with the depth of the holdback dog being less than that of the puller dog portion. A smooth curvilinear shape inhibits accidental disengagement during transistion between levels and inclined movement and assures straight-line force generation between the drive post and drive arm pivot pin when the holdback dog is utilized. An auxiliary pusher arm is also utilized for switching the carrier from one free track to the other and is urged by its own weight into a retracted non-post engaging position. Ramps are positioned for positive cam movement of the auxiliary pusher arm for engagement with or disengagement from a secondary drive post.

United States Patent [191 v De Good et al.

[ 51 Apr. 2, 1974 TROLLEY DRIVE FOR OVER AND UNDER CONVEYOR [75]Inventors: Maynard J. De Good; Wendell G.

Champion, both of Grand Rapids, Mich.

[73] Assignee: Rapistan Incorporated, Grand Rapids, Mich.

[22] Filed: Feb. 7, 1972 211 App]. No.: 224,173

Primary Examiner-Robert G. Sheridan Assistant Examiner-Richard A.Bertsch Attorney, Agent, or Firm-Price, Heneveld, l-luizenga & Cooper 57ABSTRACT The main propelling member is mounted on an overhead powertrack for selected driving engagement with carriers suspended bytrolleys on the free track. The propelling member has a depending pullerarm with a socket forming integral puller and holdback dogs engageablewith a drive post on the carrier. The upper surface of the socket isirregular with the depth of the holdback dog being less than that of thepuller dog portion. A smooth curvilinear shape inhibits accidentaldisengagement during transistion between levels and inclined movementand assures straight-line force generation between the drive post anddrive arm pivot pin when the holdback dog is utilized. An auxiliarypusher arm is also utilized for switching the carrier from one freetrack to the other and is urged by its own weight into a retractednon-post engaging position. Ramps are positioned for positive cammovement of the auxiliary pusher arm for engagement with ordisengagement from a secondary drive post.

12 Claims. 11 Drawing Figures PAIENTEUAPR 2 m4 SHEET 2 BF 5IZO NCLINEDTRACK ORTION IIYI W @2623:

FIG. 9

TROLLEY DRIVE FOR OVER AND UNDER CONVEYOR BACKGROUND OF THE INVENTIONThis invention relates to an improved power and free conveyor systemand, more particularly to an improved retractable drive mechanism.

Over and under, power and free conveyors have become widely adopted inmoving loads on carriers from one location to another. They areparticularly adapted for accumulation of carriers at selected points;transfer of the carriers from one track to another or, the transfer ofcarriers between different levels by movement up or down inclined tracksections. A particularly novel and efficient system is described in anapplication entitled TROLLEY DIVERTER, filed July 28, 1971, Ser. No.166,871 having a common assignee with this application. This applicationhas a common assignee and is incorporated herein by reference.

One significant aspect of the invention described in the aboveincorporated application is the elimination of variations in the trackspacings during switching and inclined movement while still retainingthe ability to provide accumulation. While there are proposals whichhave eliminated variations in track spacings, none have done it asefficiently in both cost and operation.

There is a need, however, for constant improvement in conveyors of thistype since installations of this type ordinarily are complex andexpensive. Thus, any reduction in areas of stress concentration andparts without sacrificing fidelity in performance is significant.

SUMMARY OF THE INVENTION In accordance with the invention, spacedtrolley and power tracks include a driven propelling member mounted onthe power track and a load carrier supported on the trolley track fortravel therealong. The load carrier includes a primary drive post whilethe propelling member includes a pivotally mounted drive arm having asocket formed therein for coupling the propelling member to the carrierdrive post. The socket opens downwardly and includes longitudinallyspaced slope pusher and holdback surfaces for engagement with the drivepost. The web or upper surface portion of the socket engages the topsurface of the drive post and is curvilinear to cam the holdback dogface when engaged with the drive post to a position whereby the forcegenerated through said drive arm is centered radially through the pivotpoint of the drive arm.

In other aspects of the invention, the carrier is supported by a pair oftrolleys, the front trolley including the main drive post and the reartrolley including a secondary drive post. An auxiliary drive is mountedon the propelling member and is spaced from the primary drive dog adistance greater than the spacing between the primary and secondarydrive posts. A constant spacing between the power and trolley tracks ismaintained throughout the conveyor and the auxiliary drive includes anauxiliary drive arm pivotally mounted thereon and urged by itsgravitational weight into a retracted position disengaged from both theprimary and secondary drive posts. An actuating means at selectedpositions along the conveyor urges the drive arm into and out of anextended position for engagement with the secondary drive post fortransmitting motion'from the propelling member to the load carrier. Innarrow aspects of the invention, both the main and secondary drive dogsare disengageable from the drive posts by actuating means adjacent thetrackway. In addition, the propelling member includes an adjustable stopfor limiting the pivotal extension of the drive arm.

The improved drive mechanism provided by the invention specificallyreduces the loading on the propelling member when the carrier is held bythe holdback dog for example as the carrier rolls down a grade. Thereduction in loading reduces wear, tear and eventual fatigue orbreakage. In addition, the operation in coupling the main or auxiliarydrive to the primary and secondary posts is positive and hence troublefree. Cam disengagement of the auxiliary drive eliminates the necessityof costly biasing mechanisms and eliminates accidentalnon-disengagement. Thus, a smoother overall operation is achieved at anoverall cost reduction.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary side elevation viewof the main drive mechanism provided by the invention wn n .vrqs ss spretion .aqs v FIGCZ is a side elevation view of the main drive mm;

FIG. 3 is a side elevation view of one of the drive arm mounting plates;

FIG. 4 is an end elevation view of the plate shown in FIG. 3;

'FIG. 5 is a cross sectional view of the plate shown in FIG. 3 takenalong line V-V of FIG. 3;

FIG. 6 is a fragmentary side elevation view of the auxiliary drivemechanism provided by the invention;

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, FIG.8 shows a conveyor 10 comprising a pair of vertically spaced tracks 12and 14 of the well-known over and under, power and free type. The tracksare of conventional enclosed construction and rigidly joined together atsuitable intervals throughout the system by a plurality of brackets 16.The conveyor is propelled by a driven chain (not shown) which travels inand is supported by power track 12.

Each load carrier (not shown) is supported from the load or trolleytrack 14 by a pair of spaced trolleys, a front or lead trolley 18(partially shown in FIG. 1) and a rear or trailing trolley 20 (partiallyshown in FIG. 6). Trolleys 18 and. 20 are connected by a rigid load bar(not shown) which is interconnected to the trolleys by a pivot. Thecarrier trolley wheels travel on rails 15, 15 of trolley track 14 shownin FIG. 8. All of the preceding described structure is conventional andwell-known to the conveyor art and a further detailed description is notconsidered necessary to an understanding of the invention.

Referring now in detail to FIG. 1, the forward or lead trolley 18 has anupstanding drive post 22. Post 22 is a primary drive post and has adownwardly flared base 24 and an inverted frusto-conical top 26 giving asomewhat hour-glass shape to post 22. Lead trolley 18 is generallyidentical to that described in the abovereferred-to copendingapplication which can be referred to for further detail.

Referring to FIG. 6, the rear or trailing trolley has an upstanding,rear drive release member 30 having an elongated top 32 and a rearwardlydepending lip 34 serving as a ramp and auxiliary drive. Under certainoperating conditions which will be described in more detail hereinafter,the rear drive release member 30 serves as a secondary drive post. Thetop of post 30 and top 32 of release member 30 are in the same generalplane. Rear drive release member 30 is located at the rear end oftrailing trolley 20 and a portion of it extends rearwardly beyond theend of the trolley. Again,

for more specific detail, reference is made to the.

above-identified copending patent application.

The drive chain (not shown) includes a plurality of intermittentlyspaced vertical and horizontally disposed rollers. The verticallyoriented rollers (FIG. 1) are preferably arranged in pairs oflongitudinally spaced sets in close proximity to each other for ridingengagement on the lower lips 42 (FIG. 8) of power track 12. Spacedlongitudinally in between each set of vertical rollers 40, 40 are onepair of horizontally disposed rollers (not shown) for engagement againstside wall portions 44 of power track 12. The rollers are preferably madeof polyurethane and this arrangement provides a quiet, smooth, positivemovement of the driven carriers as the drive chain traverses variousstraight, inclined and curved sections of the track. Any othersatisfactory drive chain construction can be used.

The propelling member includes front and rear trolley drive brackets 45and 47 (FIGS. 1 and 6). Each of the trolley drive brackets 45 and 47includes clevis 46 which forms the body of the brackets. As shown inFIG. 8, the clevis is comprised of a pair of mating plates 48a and 48b.The clevis has an upper portion 52 which projects into track 12 and isconnected to the axles of the chain rollers 40, 40 and a lower portion54 which projects below track 12 and above track 14. Either a puller armor pusher arm 62 is pivotally mounted to lower portion 54 as will bedescribed shortly.

Referring to FIGS. 35, plate 48a is shown from the side to have agenerally L-shape with the upper vertical portion when joined to thecorresponding portion of plate 48b forming portion 52 of clevis 46.Likewise the lower horizontal forms portion 54 of clevis 46. Upperportion 52 of clevis 46 includes a pair of longitudinally spacedopenings 56 which receive the axles of rollers 40, 40. The upperportions of plates 48a and 48b are joined together in a face-to-facerelationship to form upper portion 52 while the lower portions areoffset outwardly to provide a slot 58 (FIG. 8) to receive either apuller arm 60 or a pusher arm 62. The lower portion 54 of each clevisincludes a pair of openings 64 similar to openings 56. These openingsare utilized for pivotally mounting either a puller arm 60 or a pusherarm 62.

A rectangular opening 66 is provided in each plate 48a and 48b forreceipt of a small guide roller 68 which is aligned between lips 42, 42of track 12. Roller 68 rotates about a vertical axis and acts tostabilize trolleys 45 and 47 as they traverse curves and to limit sidesway. Referring to FIG. 5, each plate 480 and 48b includes an outwardlyoffset strap 70. The straps 70 provide a pair of sockets for themounting pin 72 of roller 68.

Referring now to FIG. 1, a puller arm 60 is pivotally mounted by a pin77 near its forward end 76 to the forward one of the holes 64 in thelower portion 54 of clevis 46. End 76 of puller arm 60 is described asthe forward or lead end in relation to the direction of travel which isshown by arrow A in FIG. 1. Puller arm 60 includes an opening (FIG. 2)for receipt of the pin 77. Due to the positioning of the pivot axis wellahead of the center of gravity of arm 60, the rearward or trailing endof puller arm 60 is urged downwardly by gravity. The trailing endincludes a socket 78 (FIG. 2) opening downwardly. Socket 78 is partiallyrestricted at its downwardly opening end but the fore and aft length ofthe socket is substantially greater than that of the top 26 of drivepost 22 to permit its entrance in the socket. Socket 78 and the partialrestriction of its entrance creates a socket configuration generallyconforming to the configuration of post top 26. The longitudinal widthof the socket entrance is less than the longitudinal length of the driverelease 30 of rear trolley 20 and hence non-complementary therewith sothat puller arm 60 is incapable of engaging the rear or secondary drivedog 20.

The rear portion of socket 78 has an inclined wall or face 80 which actsas a drive dog when engaged with top 26 of drive post 22 to pull thecarrier along trolley track 14. The forward end of socket 78 includes agenerally similar but oppositely inclined wall or face 82 which acts asa holdback dog when engaged by top 26 of post 22 to restrain the loadcarrier from uncontrolled forward movement relative to puller arm 60.The upper surface or ceiling portion 84 of socket 78 has an irregularcurvilinear shape particularly adapted to position puller arm 60, wheneither drive face 80 or holdback face 82 is engaged with top 26 of drivepost 22, such that the force generated between drive post 22 and pullerarm 60 acts in a straight line through pivot pin 77. This arrangementeliminates the generation or forces acting to pivot the puller arm up ordown with respect to the drive post 22. It also reduces the shear forcesacting on the pin 77. The irregular curved configuration also inhibitsaccidental disengagement during transitional movement of the carriersfrom or to an inclined track portion the details of which will bedescribed hereinafter.

Describing the socket in greater detail, the upper surface 84 of thesocket has a rearward portion 85 having a fore and aft length greaterthan the fore and aft length of the top of the drive post 26 (FIGS. 1and 2). The forward portion 86 of the upper surface is downwardlyoffset, reducing the depth of the socket adjacent the holdback face 82.These two portions are connected by a smoothly secured transitionportion 87 which acts to smoothly cam the puller arm 60 about the post22 as the post shifts for and aft in the socket.

Both forwardly and rearwardly of the entrance to socket 78, the lowerface of puller arm 60 is inclined upwardly creating both a forward ramp86 and a rearward ramp 88. A pin 89 projects laterally from puller arm60 adjacent its rearward end and above socket 78.

.Rotatably mounted on the outer end of pin 89 is a cam roller 90. Roller90 is selectively engageable with a rail 92 which includes a rampportion 94 which cams roller 90 and puller arm 60 upwardly to aretracted nonengaging position with respect to drive post 22. In otherinstances, a similar rail 96 (FIGS. 9, 10, and 11) is provided to lockthe drive arm in extended portion and to prevent accidental separationof puller arm 60 from the drive post 22. The terminal ramps of the rails96 will be inclined oppositely that of the rails 92 since they actoppositely upon the drive arm.

The arm 60 has an upstanding forward end 76 ahead of clevis 46 whichacts as a stop when arm 60 is disengaged from trolley 18 to limit thedownward extension of arm 60. An adjustable set screw 91 with anonmetallic, preferably polyurethane, head 93 provides adjustment forthe stop and prevents metal-to-metal contact between arm 60 and clevis46. The maximum extension of the arms is illustrated in broken lines inFIG. 1 and indicated by the letter B.

Referring now to FIGS. 6 and 7, the rear trolley 47 of the propellingmember is comprised of a clevis 46 and pusher arm 62 mounted to thedrive chain. The forward end of arm 62 includes an inclined drive face100 'for engagement with the auxiliary drive 34 and rear drive releasemember 30 on rear trolley of the load carrier. The auxiliary drive face100 is spaced rearwardly from the face 80 forming the drive dog ofpuller arm 60 a distance greater than the spacing between post 22 andauxiliary drive 34. Thus, the spacing of each pair of brackets 45 and 47is greater than the spacing between the leading and trailing trolleys 18and 20 of a load carrier.

Pusher arm 62 is pivotally mounted at 102 by a pin 104 received throughthe rearward opening 64 of clevis 46. The pin 104 is forward of thecenter of gravity of pusher arm 62 whereby gravity biases the pusher arm62 into raised or retracted position. A pin 106 is mounted in theforward opening 64 and acts as a stop against the forward end of arm 62to limit the retraction of arm 62. Preferably, arm 62 is stopped in ahorizontal retracted or non-drive position, as shown in FIG. 6 in solidlines. In retracted position, the lowermost edge 108 of pusher arm 62 isspaced vertically above the upper extremity 32 of rear drive release 30and above the top 26 of drive post 22. Thus, unless positive action istaken to pivot pusher arm 62 clockwise to lower drive face 100 thepusher arm 62 remains retracted. On the other hand, the gravitationalbias of puller arm 60 is such that unless affirmative action is taken toraise it into retracted position, illustrated in broken lines in FIG. 1and indicated by the letter C, the normal position of puller arm 60 isextended into drive position.

Projecting laterally from pusher arm 62 adjacent its rearward ortrailing end is a pin 109. On the outer extremity of pin 109 is mounteda cam roller 110 as shown in FIG. 8. Pin 109 and cam roller 110 areidentical to pin 89 and cam roller 90 described above with respect topuller arm 60. Cam roller 110 is adapted for selective engagement with arail 112 (FIG. 6) having a ramp portion 114 at its forward end inclinedupwardly to shift pusher arm 62 into the inclined position shown in FIG.6 so that auxiliary drive face 100 is positioned for driving engagementwith auxiliary drive 34 on the trailing trolley 20 of the load carrier.

A second rail section 116 is positioned upstream from the termination ofrail 112 and includes an upwardly extending downwardly sloped ramp 118at its leading end for camming engagement with roller 1 10 to positivelyshift pusher arm 62 into retracted position. The specific details andfunctioning of rails 112 and 116 will be described hereinafter morefully. It should be noted at this point however that the lateralprojection of pin 109 and roller 1 10 is opposite to pin 89 and camroller mounted on puller arm 60 so that rollers 90 are actuated only bythe rails 92 and 96 and the rollers are actuated only by the rails 112and 116.

Over and under conveyors of the type with which this invention isconcerned are so designed as to form a closed loop such as that loop 120schematically illustrated in FIG. 9. Such conveyors normally incorporateone or more secondary or spur tracks 122. Such secondary tracks may beused for trolley accumulation or as a diversion through a secondaryprocessing area or for any other reason. Frequently, it is necessarythat the track change elevation, necessitating inclination of portionsof the track as schematically illustrated at 124 and 124a in FIG. 9.This invention in one aspect is particularly concerned with thepropelling of the trolleys at the switches 126 and 1260 where thesecondary and primary tracks come together. In a second aspect,particular concern is given for propelling the trolleys at the inclinedportions 124 and 124a of the track.

In application Ser. No. 166,87l, of which reference has previously beenmade, a construction is disclosed by which trolleys can be switchedbetweeen main and auxiliary tracks and moved through inclined trackareas without varying the spacing between the power and trolley tracks.This is true whether or not the auxililary tracks are powered. Thisinvention provides an improvement in the construction taught in thatapplication.

For purposes of this description it is assumed that a load carrier istraveling along loop 120 in the direction of arrow D propelled by pullerarm 60 with the arm in drive position generally as shown in solid-linesin FIG. 1. Pusher arm 62 on the other hand is in a retracted position asillustrated in solid lines in FIG. 6. Assuming that the carrier is to bediverted onto loop 122 at switch 126, the switch is actuated by shiftinga tongue or other conventional means to deflect the forward trolley 18of the load carrier from main track 120 to the spur track 122. As thelead trolley is forced laterally by the tongue, post 22 slides sidewaysout of socket 78 releasing it from drive face 80. This results indisengagement, leaving the load carrier stalled partially on andpartially off main track 120.

The auxiliary pusher arm 62 now takes over and completes the shunting ofthe load carrier onto the auxiliary or spur track. Since pusher arm 62is normally retracted and inoperative, it must be shifted to anoperative position to do this. This is accomplished by a rail 112mounted on the power track 12 (See FIG. 6 and 9). The rail 112 ismounted on the side of the power track to intercept cam roller 1 10 onthe pusher arm 62. The leading end of rail 112 is sloped downwardly toform a ramp 114 which acts to pivot arm 62 into its extended positionfor engagement of pusher face 100 with the rear drive 34 of trolley 20.The length of rail 112 is such that this occurs at a point just prior toor simultaneously with the disengagement of the puller arm 60 from post22. Because of the spacing between drive face 80 and face 100, there isa short interval during which the load carrier remains stationary or atleast slows down since it will ordinarily have some momentum. However,as soon as pusher arm 62 engages the rear end of the trailing releasemember 30, movement of the load carrier will be reinitiated and willcontinue until the rear trolley 20 has been pushed off the main track120. During this operation, the rear or trailing release memberfunctions as an auxiliary drive post. After this has occurred, rail 112is terminated permitting the pusher arm 62 to retract by its own weight.It will be noted that the cam roller 90 on the puller arm 60, since itprojects oppositely from the roller 110 on the pusher arm, is notaffected by rail 112. Because the working environment of :many conveyorsof this type involves materials which tend to prevent the free movementor movable parts, it is desirable to provide means to provide positiveoperation. Examples of such circumstances are dirt, spray baths andcontact with corrosive chemicals. To insure positive retraction of thepusher arm 62, a short rail 116 is provided with an upturned lead rampto forcibly retract the arm, if necessary.

The forward trolley of a diverted load carrier, after it has been pushedoff the main track by pusher arm 62, is positioned such that the nextapproaching arm (not shown) on the chain of the spur power track willengage drive post 22 of the load carrier and pull it along the spurtrack. If the spur track is non-powered, the effect of the auxiliarydrive of the main track is to push the load carrier to a position wheregravity will cause the load carrier to move away from the main track, atleast sufficiently to clear the switch area. All of these details areconventional and the preferred apparatus is described in the aboveidentified copending application.

Where the switch is one at which load carriers enter the main track 120from spur track 126, (i.e. switch 126a) the procedure is reversed. Herethe puller arm 60 of the spur track will release the load carrierjustbefore it reaches the switch because the arm and socket will shiftlaterally with respect to the load carrier. Here a ramp 112a (FIG. 9) isprovided on the spur track to activate the following auxiliary pusherarm on the spur track chain. The auxiliary pusher arm will push the loadcarrier. moving its forward trolley onto the main track where its post22 will be captured by the next passing puller arm on the drive chain ofthe main conveyor 120.

It will be recognized that suitable coordination devices must beprovided to prevent movement of a load carrier on to the main track onlywhen an empty drive dog on the main track is approaching. Such deviceshave long been used in this type of conveyor and are, therefore, notillustrated or described here.

A significant improvement of this invention is the elimination ofadditional structure required to hold pusher arm 62 in retractedposition. Thus, in accordance with the invention, pusher arm 62 remainsin a normal retracted position as a result of its gravitational weightin accordance with its unique mounting to clevis 46. When it isextended, only the pusher arm 62 is positively cammed by the rail 112and ramp 114 into a drive engaging position.

At inclined track sections, (FIGS. 10 and 11) it is desirable to lockpuller arm 60 into engagement with drive dog 26. This is accomplished bya rail 96 (FIGS. 9-11) similar to rail 116 mounted on the opposite sideof the power track 12. Rail 128 is spaced slightly above cam roller onpuller arm 60 to prevent unintentional separation of socket 78 fromdrive post 22. This prevents inadvertent upward pivoting of the pullerarm to release the post due to heavy loads. Again, the use of a rail andcam roller eliminates the necessity for varying track spacing. The leadramp of the rail 96 is inclined oppositely from that of the ramp 92because it is designed to shift the drive arm in the opposite direc-U011.

There may be situations in which it is desired to provide positivedisengagement between puller arm 60 and drive post 22. For example, on aspur track after the carrier has been brought to a work processingstation. it may be desired to automatically leave it at that point. Aretracting rail 92 (FIGS. 1 and 9) is utilized in these instances.Preferably rail 92 has a ramp 94 at its leading end for camming roller90 and arm 60 up out of engagement with drive post 22. Rail 92 canextend as long as positive disengagement is preferred. Once rail 92 isterminated, puller arm 60 will pivot into a drive engaging position byits own weight. Selective disengagement can also be achieved by theutilization of movable ramps in accordance with the skill of the art.Accumulation is also provided by the apparatus of the invention inaccordance with the teachings of the referred to copending applicationincorporated herein by reference.

Referring now back to FIGS. 10 and 1 1, FIG. 10 illustrates the positionof drive post 26 and puller arm 60 during descent of a carrier down aninclined track portion 124a. During descent, the load carrier by itsgravitational weight will generally urge the movement of the carrierdown the incline at a rate faster than the movement of the drive chainto which puller arm 60 is connected. Thus, the arm 60 shifts itsjuncture from propulsion to braking. Without some type of holdbackmeans, the carrier would indeed run away from puller 60 and perhapscause substantial damage at some point down the incline. However, socket78 in addition to forming a drive face 80, also includes a holdback face82.

As the carrier moves onto or off from an incline portion, it passesthrough a transition at the track juncture, between a level trackportion and incline track portion indicated by reference numeral in FIG.10. At this transitional point, the upper end 26 of drive post 22 exertsa rotational force on puller arm 60 as it passes or traverses agenerally arcuate path from the level direction of travel to an inclinedirection of travel. By the same token at the bottom of an incline, theupper end of end 26 of post 22 tends to exert a similar force. In someinstances, during movement through this transition point, there has beennoted a tendency due either to this rotational force or to irregularityof travel or other conditions for the puller arm 60 to be pushed upwardswhereby post 22 is not in engagement with the upper ceiling or roofportion 84 of socket 78. In a conventional socket opening wherein upperportion 84 defines a smooth arcuate surface, the carrier may acceleratesuch that the post 22 strikes holdback face 82 while the upper surfaceof post 22 is not in contact with upper surface 84. To avoid this, thisinvention provides a surface 84 wherein the ceiling of the holdbackportion 82 of socket 78 is offset downwardly forming a ceiling portion86a producing a socket of lesser depth. This results in a reducedbearing or impact causing wear. It can, in some cases result in forcespivoting the arm into disengagement. It can also result in repeatedimpacting between arm and post, accelerating wear. The transitionalportion intermediate these two ceiling portions is curved downwardly tocam against drive post 22 to inhibit separation during transition from alevel or incline portion to the other. In addition, the offsetting ofdrive face 80 vertically from holdback face 82 positions puller arm 60at a slightly different angle about pivot pin 77 as that the forcegenerated between frusto-conical top 26 of drive post 22 and holdbackface 82 is centered through pin 77 to eliminate or at least greatlyreduce any moment arm created about pin 77. In conventional power andfree conveyors of this type, the forward end 76 of puller arm wasgenerally in abutment with some portion of the body of the power trolleyto prevent further rotation. However, the vector of forces generated bythe drive post and puller arm tended to create severe moments about thepivot pin causing accelerated fatigue and in some instances failure. Byoffsetting the vertical level of the drive face 80 and holdback face 82,this problem can be significantly reduced of if the angle of descent isproperly selected, to match the socket configuration, completelyalleviated.

Referring now to FIG. 1 l, the carrier is shown being conveyed up anincline 124. Again, depending on the configuration of socket 78, avariety of force vectors can be developed about pin 77. By positioningceiling portion 85b of drive face 80 slightly above ceiling 86a ofholdback face 82, puller arm 60 is rotated or positioned slightly moretoward the horizontal when in a pulling position than when in holdbackposition. This tends to reduce the moment acting through power driverollers 40, 40 connected to the drive chain. Also, moment forces frompost 22 are resolved between surfaces 82 and 86 of arm 60 and notbetween stop 93 and clevis 46.

Of additional interest, it will be appreciated that when puller arm 60first begins engagement with drive post 22 on a level surface such asshown in FIG. 1, the puller arm is pulled up over drive post 22 until itclears the lowermost point of holdback surface 82 wherein puller arm 60drops down over the upper end 26 of drive post 22. The abruptness of thevertical movement is reduced somewhat since it will first strike the topof post 22 in the holdback area. The upper surface will then be cammedalong into surface 85b, thus easing it into its fully lowered drivingposition before drive face 80 strikes the post.

It will be appreciated that this invention provides a simple anddependable solution to the problems encountered in providing loadcarrier switching, accumulation, and ascent or descent on an inclinedtrack portion with a safety lock on the inclines. The utilization of asecondary pusher arm 62 which is gravitationally urged into a retractedposition simplifies the overall structure thereby reducing the overallcost. In addition, the utilization of a pair of identical clevises 46 toform the body of the bracket on the chain is adaptable for use witheither puller arm 60 or pusher arm 62. This likewise simplifies thepower chain arrangement and reduces cost.

Although but one embodiment has been shown and described in detail, itwill be obvious to those having ordinary skill in this art that thedetails of construction of this particular embodiment may be modified ina great many ways without departing from the unique concepts presented.It is, therefore, intended that the invention is limited only by thescope of the appended claims rather than by the particular details ofconstruction shown, except as specifically stated in the claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows.

1. A power and free conveyor having trolley and power tracks spaced aconstant distance from each other throughout the system and a drivenpropelling member mounted in said power track, at least one elongatedload carrier supported on said trolley track for travel therealong, saidload carrier having a primary drive post at its leading end andsecondary drive post at its trailing end, a primary drive on saidpropelling member adapted to engage said primary drive post, anauxiliary drive on said propelling member spaced from said primary drivea distance greater than the spacing between said primary and secondarydrive posts, the improvement in said conveyor comprising: said auxiliarydrive having a pusher arm, said pusher arm having a weighted end and adrive end and means pivotally mounting said pusher arm intermediate saidends to said auxiliary drive, said pusher arm urged by its weighted endinto a retracted position disengaged from both said primary andsecondary drive posts; actuating means at selected positions along saidconveyor for engaging said pusher arm to urge said pusher arm into anextended position and holding said pusher arm in said extended position;said pusher arm, when so extended, being engageable with said secondarydrive post for transmitting motion from said propelling member to saidload carrier.

2. A conveyor as described in claim 1 wherein said actuating meansincludes a rail means positioned adjacent said power track for engagingsaid weighted end of said pusher arm, said rail means including a rampportion inclined upwardly for engagement with said weighted end of saidpusher arm to urge said pusher arm into said extended position, saidrail means including a second portion extending downstream from saidramp portion, said second portion being generally parallel to thedirection of movement of said auxiliary drive and engageable with saidweighted end to hold said pusher arm in said extended position.

3. A conveyor as described in claim 2 wherein said actuating meansincludes a second rail means defining a ramp portion spacedlongitudinally from said first rail means, said second ramp portionbeing inclined downwardly for engagement with said weighted end of saidpusher arm to urge said pusher arm into said retracted position toprovide positive disengagement by said pusher arm from said secondarydrive post.

4. A conveyor as described in claim 3 wherein said weighted end of saidpusher arm includes a laterally projecting pin having a cam rollermounted on the end for engagement with said rail means.

5. A conveyor as described in claim 1 wherein said conveyor includesinclined track portions to provide relative vertical ascent and descentof said load carrier; said primary drive including a puller armpivotally mounted thereon and urged by its gravitational weight into anextended drive engaging position, said puller arm including a downwardlyopening socket having one wall defining a drive dog adjacent itsrearward end and a second wall defining a holdback dog adjacent itsforward end, said walls being adapted for engagement with said primarydrive post, said socket being noncompatible with said secondary drivedog, the upper surface of said socket having -a downwardly offsetportion adjacent said second wall to limit the distance said puller armseats down over the primary drive post when the post is in engagementwith said second wall; said upper surface having a smooth transitionsection between its forward and rearward portions for camming saidpuller arm on said drive post; said forward and rearward portions ofsaid upper surface positioning said puller arm to provide straight-lineforce generation through said puller arm pivot.

6. A conveyor as described in claim wherein said conveyor includesadditional actuating means at selected positions along said conveyor forengaging said puller arm to urge said puller arm into a retractednondrive engaging position; and means for preventing disengagementbetween said puller arm socket and primary drive post during movement ofsaid load carrier along said inclined track portions.

7. A conveyor as described in claim 6 wherein said additional actuatingmeans includes a rail means positioned adjacent said power track forintercepting a portion of said puller arm, said rail means including aramp portion inclined upwardly for engagement with said portion of saidpuller arm to urge said puller arm upwardly into a retracted, non-driveengaging position, said rail means including a second portion extendingdownstream from said ramp portion, said second portion being generallyparallel to the direction of movement of said puller arm and engageablethereby to hold said puller arm in said retracted position, said meansfor preventing disengagement between said puller arm socket and primarydrive post comprising a second rail means similar to said second portionof said rail means spaced slightly above said portion of said puller armwhen said puller arm socket is engaged with said primary drive post toprevent disengagement between said puller arm socket and primary drivepost.

8. A conveyor as described in claim 5 wherein said propelling memberincludes a front and rear longitudinally spaced clevis interconnectingsaid puller and pusher arms to said power track, each of said clevismembers being identical and adapted for receipt of either of said pulleror pusher'arm.

9. A conveyor having a power track and a propelling member movable alongsaid power track; a puller arm having a lead end and a trailing end,said puller arm pivotally mounted adjacent its lead end to saidpropelling member; a load carrier movable along a load track, saidcarrier having a drive post projecting towards said puller arm, saidpuller arm at its trailing end having a socket formed therein to capturesaid drive post, said socket being longer than the fore and aft lengthof said drive post, said socket defining integral rearward drive andforward holdback faces spaced longitudinally from each other to provideand inhibit respectively movement of said carrier with respect to saidpuller arm when said drive post is captured in said socket, said sockethaving an upper surface extending between said drive and holdback faces,said upper surface having forward and rearward portions, the improvementcomprising: said forward portion of said upper surface of said socketbeing downwardly offset adjacent said holdback face to restrict thedepth or entry of said drive post into said socket when said holdbackface is en gaged with said drive post sovthat the pivot angle of saidpuller arm relative to said power track is larger when said arm isoperable to pull said load carrier than when said puller arm is operableto hold back said load carner.

10. A conveyor as described in claim 9 wherein said upper surface ofsaid socket has a smoothly curved transition section between the forwardand rearward portions thereof for camming said puller arm about the topof said drive post as said drive post shifts forwardly or rearwardlywithin said socket.

l l. A conveyor as described in claim 10 wherein said rearward portionof said upper surface has a fore and -aft length at least equal to thatof the top of said drive post to permit said forward portion of saidupper surface to rest on the top of said drive post when said drive postand said rearward drive faces are engaged.

12. A conveyor as described in claim 11 wherein a pin provides saidpivotal mounting of said puller arm to said propelling member and saidpivot angle of said puller arm both when said drive post is engaged withsaid drive face and when engaged with said holdback face is such thatthe forces generated about said pin pass through said pin eliminatingbending movements about said pin.

. U NR'TED STATES PATENT OFFICE @ERTEFECATE OF CORRECTION Patent No. 3800' "709 Dated April 2 1974 Inventor) Mag'ns rd J. DeGood, et a1.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

a Column 7 Line 25:

After "approaching" insert puller Column 9, Line 10:

"as'" should read so Signed sealed this 10th day of September- 197%.

(SEAL) Attes't:

MCCOY M. GIBSON, JR. C. LARSPLALJL DANN Attesting Officer Commissionerof Patents

1. A power and free conveyor having trolley and power tracks spaced aconstant distance from each other throughout the system and a drivenpropelling member mounted in said power track, at least one elongatedload carrier supported on said trolley track for travel therealong, saidload carrier having a primary drive post at its leading end andsecondary drive post at its trailing end, a primary drive on saidpropelling member adapted to engage said primary drive post, anauxiliary drive on said propelling member spaced from said primary drivea distance greater than the spacing between said primary and secondarydrive posts, the improvement in said conveyor comprising: said auxiliarydrive having a pusher arm, said pusher arm having a weighted end and adrive end and means pivotally mounting said pusher arm intermediate saidends to said auxiliary drive, said pusher arm urged by its weighted endinto a retracted position disengaged from both said primary andsecondary drive posts; actuating means at selected positions along saidconveyor for engaging said pusher arm to urge said pusher arm into anextended position and holding said pusher arm in said extended position;said pusher arm, when so extended, being engageable with said secondarydrive post for transmitting motion from said propelling member to saidload carrier.
 2. A conveyor as described in claim 1 wherein saidactuating means includes a rail means positioned adjacent said powertrack for engaging said weighted end of said pusher arm, said rail meansincluding a ramp portion inclined upwardly for engagement with saidweighted end of said pusher arm to urge said pusher arm into saidextended position, said rail means including a second portion extendingdownstream from said ramp portion, said second portion being generallyparallel to the direction of movement of said auxiliary drive andengageable with said weighted end to hold said pusher arm in saidextended position.
 3. A conveyor as described in claim 2 wherein saidactuating means includes a second rail means defining a ramp portionspaced longitudinally from said first rail means, said second rampportion being inclined downwardly for engagement with said weighted endof said pusher arm to urge said pusher arm into said retracted positionto provide positive disengagement by said pusher arm from said secondarydrive post.
 4. A conveyor as described in claim 3 wherein said weightedend of said pusher arm includes a laterally projecting pin having a camroller mounted on the end for engagement with said rail means.
 5. Aconveyor as described in claim 1 wherein said conveyor includes inclinedtrack portions to provide relative vertical ascent and descent of saidload carrier; said primary drive including a puller arm pivotallymounted thereon and urged by its gravitational weight into an extendeddrive engaging position, said puller arm including a downwardly openingsocket haVing one wall defining a drive dog adjacent its rearward endand a second wall defining a holdback dog adjacent its forward end, saidwalls being adapted for engagement with said primary drive post, saidsocket being non-compatible with said secondary drive dog, the uppersurface of said socket having a downwardly offset portion adjacent saidsecond wall to limit the distance said puller arm seats down over theprimary drive post when the post is in engagement with said second wall;said upper surface having a smooth transition section between itsforward and rearward portions for camming said puller arm on said drivepost; said forward and rearward portions of said upper surfacepositioning said puller arm to provide straight-line force generationthrough said puller arm pivot.
 6. A conveyor as described in claim 5wherein said conveyor includes additional actuating means at selectedpositions along said conveyor for engaging said puller arm to urge saidpuller arm into a retracted non-drive engaging position; and means forpreventing disengagement between said puller arm socket and primarydrive post during movement of said load carrier along said inclinedtrack portions.
 7. A conveyor as described in claim 6 wherein saidadditional actuating means includes a rail means positioned adjacentsaid power track for intercepting a portion of said puller arm, saidrail means including a ramp portion inclined upwardly for engagementwith said portion of said puller arm to urge said puller arm upwardlyinto a retracted, non-drive engaging position, said rail means includinga second portion extending downstream from said ramp portion, saidsecond portion being generally parallel to the direction of movement ofsaid puller arm and engageable thereby to hold said puller arm in saidretracted position, said means for preventing disengagement between saidpuller arm socket and primary drive post comprising a second rail meanssimilar to said second portion of said rail means spaced slightly abovesaid portion of said puller arm when said puller arm socket is engagedwith said primary drive post to prevent disengagement between saidpuller arm socket and primary drive post.
 8. A conveyor as described inclaim 5 wherein said propelling member includes a front and rearlongitudinally spaced clevis interconnecting said puller and pusher armsto said power track, each of said clevis members being identical andadapted for receipt of either of said puller or pusher arm.
 9. Aconveyor having a power track and a propelling member movable along saidpower track; a puller arm having a lead end and a trailing end, saidpuller arm pivotally mounted adjacent its lead end to said propellingmember; a load carrier movable along a load track, said carrier having adrive post projecting towards said puller arm, said puller arm at itstrailing end having a socket formed therein to capture said drive post,said socket being longer than the fore and aft length of said drivepost, said socket defining integral rearward drive and forward holdbackfaces spaced longitudinally from each other to provide and inhibitrespectively movement of said carrier with respect to said puller armwhen said drive post is captured in said socket, said socket having anupper surface extending between said drive and holdback faces, saidupper surface having forward and rearward portions, the improvementcomprising: said forward portion of said upper surface of said socketbeing downwardly offset adjacent said holdback face to restrict thedepth or entry of said drive post into said socket when said holdbackface is engaged with said drive post so that the pivot angle of saidpuller arm relative to said power track is larger when said arm isoperable to pull said load carrier than when said puller arm is operableto hold back said load carrier.
 10. A conveyor as described in claim 9wherein said upper surface of said socket has a smoothly curvedtransition section between the forward and rearward portions thereof forcamming said puller arm about the top of said drive post as said drivepost shifts forwardly or rearwardly within said socket.
 11. A conveyoras described in claim 10 wherein said rearward portion of said uppersurface has a fore and aft length at least equal to that of the top ofsaid drive post to permit said forward portion of said upper surface torest on the top of said drive post when said drive post and saidrearward drive faces are engaged.
 12. A conveyor as described in claim11 wherein a pin provides said pivotal mounting of said puller arm tosaid propelling member and said pivot angle of said puller arm both whensaid drive post is engaged with said drive face and when engaged withsaid holdback face is such that the forces generated about said pin passthrough said pin eliminating bending movements about said pin.